Answers

2015-07-03T23:56:21+05:30
(a-b)^2=a^2 - 2*a*b + b^2
(3x-7y)^2=(10)^2
9x^2 - 2*3x*7y + 49y^2 = 100
9x^2 - 2*21*1 + 49y^2 = 100
9x^2 + 49y^2 = 100-42
=58.
0